text: PROX is an acronym for PReferential OXidation, that refers to the preferential oxidation of carbon monoxide in a gas mixture by a catalyst. It is intended to remove trace amounts of CO from H/CO/CO mixtures produced by steam reforming and water-gas shift. An ideal PROX catalyst preferentially oxidizes carbon monoxide (CO) using a heterogeneous catalys<nowiki/>t placed upon a ceramic support. Catalysts include metals such as platinum, platinum/iron, platinum/ruthenium, gold nanoparticles as well as novel copper oxide/ceramic conglomerate catalysts.